This invention relates generally to a method and system for digitizing signals and, more particularly, to a method and system for extracting time and amplitude information from an analog signal and providing separate digital representations thereof.
Signal digitizing circuits such as analog to digital converters are used in a variety of applications, particularly in communications. For example, speech or other analog signals are increasingly represented by digital values for storage, transmission, or the like. Of course, the original analog signal must be converted to a digital form prior to such storage or transmission.
One common way to digitize an analog signal is to sample the signal at a regularly repeating sampling interval, determine the magnitude of each sample, and represent the magnitude in a digital form such as binary or binary coded decimal. The digital representation of the analog signal thus is a sequence of magnitudes of the signal, each expressed as a binary word or in some other suitable digital format, where the time between each digital magnitude is uniform and is a function of the rate of the clock used to sample the analog signal.
It will be appreciated that with such an analog-to-digital conversion system, to achieve any useful degree of accuracy in signal reproduction, the clock or sampling rate of the system must be considerably higher than the highest expected frequency of the analog signal. Otherwise, complete half-cycles or cycles of the analog signal may be lost, or at least insufficient information about signal reversals will be available in digital form to accurately reproduce the analog signal. It will also be appreciated that the number of samples will be a function of the clock rate and not the signal being digitized. Therefore, an audio signal having a wide dynamic frequency range will have many more samples per cycle for signals at the low frequency end than for signals at the high frequency end.